Sarjahybridit

Sarjahybridit (Finnish: sarja-hybridi) refer to a class of hybrid propulsion systems used in some vehicles. In a sarja-hybridi, the internal combustion engine does not drive the wheels directly; instead it powers a generator that charges a battery, and an electric motor draws power from the battery to drive the wheels.

The drivetrain decouples engine speed from wheel torque, allowing the engine to run in its most efficient operating point while the electric motor handles propulsion. The battery can be charged by the engine’s generator and by regenerative braking. Plug-in versions can also be charged from external sources and may be designated as range-extended electric vehicles.

Compared with parallel hybrids, sarjahybridit typically experience different efficiency characteristics, with potential losses from multiple energy conversion stages but the ability to optimize engine operation for emissions and performance in urban driving. Their design can simplify the powertrain layout and allow flexible packaging, though at the cost of added complexity, weight, and system cost. Energy-management software plays a crucial role in minimizing losses and determining when to run the engine versus rely on stored electricity.

The term is primarily used in Finnish technical literature; in English-language sources the concepts are usually described as series hybrids or range-extended electric vehicles. Related topics include hybrid electric propulsion, series vs. parallel hybrid architectures, and energy-management strategies for electrified powertrains.